Device for controlling the idling operation of spark-ignition internal combustion engines with fuel injection



March 22, 1960 w STAEGE 2,929,370

DEVICE FOR CONTROLLING THE IDLING OPERATION OF SPARK-IGNITION INTERNAL COMBUSTION ENGINES WITH FUEL INJECTION Filed 001 16, 1957 INVEN TOR. Ive/um 9W 1mm 5. Wm M United States Patent DEVICE FOR CONTROLLING THE IDLING OPER- 'ATION F SPARK-IGNITION INTERNAL COM- BUSTION ENGINES WITH FUEL INJECTIGN Werner Staege, Freudenstadt, Germany, assignor to Kugelfischer Georg Schaefer & Co., Schweinfurt, Germany, a

Application October 16, 1957, Serial No. 690,574

6 Claims. (Cl. 123-139) In an internal combustion engine of the spark-ignition type the quantity of fuel injected into each individual cylinder for every working stroke is varied as a function of the speed of the engine and of the position of the air intake throttle. This makes it possible, when the vehicle is driven under conditions under which the driving wheels are driving the engine crankshaft, as is the case, for example, on downgrades, with the fuel supply system in its idling position, to cause the delivery of the fuel injection pump to be reduced to zero as a function of the engine speed, this being possible until a predetermined rotary speed is exceeded which is higher than the minimum speed required for idling. This is a definite advantage from an economic point of view. However, the accompanying disadvantage has to be taken into account which resides in the fact that, when the engine, beginning With the operating condition just mentioned, has to be operated with fuel injection, there will be observed a transition period during which the fuel/ air mixture is too lean, it not being until the end of this transition period that an ignitable mixture is obtained. The result 35 of this condition is that the engine misfires, that it develops engine knock and the engine generally operates in a jerky irregular manner. The fact that the fuel/ air mixture is too lean in the above-mentioned transition range has to be attributed to the fact that in View of the reduction in the quantity of fuel injected into the cylinders as a function of engine speed the rate of air flow necessary for idling, which fiow is determined by the limit imposed on the opening movement of the air thrott le, is maintained, the result being that, while the quan-. tity of fuel injected is being increased from zero, there is already a considerable rate of air flow which is again increased considerably by the air throttle being opened further. These conditions are even aggravated by the fact that the rate of air flow increases more rapidlythan the rate of fuel injection.

. It' is one object of the present invention to eliminate the aforementioned drawbacks, this being done, accordiug to the invention, by providing, in association with the air, intake throttle which is capable of being closed completely in its idling position, a per se known bypass adapted to supply the air required for idling, the arrangement being such that the air throttle, when moved a direction towards its closed position can assume a, closed position and can move further, while still remaining closed, until an extreme position is reached in which the control system of the fuel injection pump which is positively connected with the air throttle can assume a position in which the delivery of the fuel injection pump is interrupted upon a predetermined speed being exceeded. Now, when the rate of fuel injection is again increased from zero, the predetermined rate of air flow associated with the idling position will first be maintained. As a result, an ignitable fuel/air mixture will be obtained with this rate of air flow, the transition range in which the fuel/air mixture is too lean having thus been shortened considerably.

7 These and other objectives and advantages of the invention will be apparent during the course of the following specification, when read in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic showing of a preferred embodiment of a control system according to the invention, a certain operating position of the fuel injection control system being shown;

Figs. 2 and 3 show two different positions of theintake air throttle during idling operation of the engine; and

Fig. 4 represents a graph in which the rate of fuel injection q has been plotted over the engine speed It for a number of different positions of the air throttle.

In the exemplary embodiment, shown in Fig. 1, of a system adapted to control the rate of fuel injection as a function of both engine speed and air intake throttle position, there is provided a governor shaft 1 whose angular position depends on a torque imposed on the shaft in response to the speed ofv the engine against the action of an opposing restoring force, the said governor shaft I carry ing an axially movable control cam. The said torque, which is'a function of engine speed, may, for example;'be imposed on the governor shaft 1 in a per se known manner by means of a magnetic clutch 21 comprising a shortcircuited rotor 24 driven by the engine and a coaxially arranged permanent magnet 22 carried by the governor shaft 23 as shown in more detail in US. Patent 2,858,-

a 822. The adjustment member 3 for the fuel injection pump 20 cooperates with a cam body 2 the shape of the peripheral surface of which has been determined from a function that has been established in any suitable manner. The axial positions of the cam body 2 are determined by the positions of a member adapted to engage the cam body and to change its position along the cam, the said member, in the embodiment of Fig. 1, being a bell-crank lever having a first arm 4 the free end of which isin sliding engagement with a peripheral groove 6 of the cam body, and a second arm 5 which is connected to the adjusting lever 8 of the intake air throttle 9 by means of a link 7 which is axially movable by means of accelerator 21. In the embodiment of Fig. 1, the throttle member 9 is in the form of a rotary valve. Provided in the body 10 of thisrotary valve is a bypass 11 which is so dimensioned or adapted to be adjusted by means of a regulating screw 12- in such a manner that it will just allow that amount of air to pass through that is necessary to provide for idling operation of the engine. It is possible to continue the rotation of the rotary throttle member 9 past its fully closed position shown in Fig. 3 (position 11 into a position ca shown in Fig. 2. It will be understood that the flow of air passing through the valve body will remain unchanged when the throttle member 9 is moved from the position ca to the positiona in which the throttle member will still just close the valve passage proper. In its idling position, which is determined by a positive stop, the throttle member 9 is in the position n as shown in Fig. 2. Under these conditions, the cam body 2 is in such a position that its peripheral groove 6 is in the position n indicated in Fig. 1. With the partsnamed in this position, the peripheral surface of the cam body 2, when adjusted in response to changes in engine speed, will move the fuel injection pump adjusting member '3 in such a manner that, when the speed of the engine, due to the crankshaft being driven by the vehicle wheels on a downgrade, rises above a speed In (which is the speed required for the maintenance of proper idling operation) up to a speed n the quantity of fuel injected per cylinder Ii3 reduced to zero as indicated by curve a in the chart of ig. 4. v Now, if it is intended, starting with the speed n; or

gine with fuel injection being resumed, the throttle member will have to be moved from its position a into its positiona or even further into any of the possible positions :1 to ca this causing the cam body 2 to be displaced in the direction of arrow 14 in'Fig. l'fro'm position a until the respective position a or a or a of the peripheral groove 6' is reached. During this action, the flow of air required for the idling of the engine, pass ing through the bypass 11, will first remain unchanged because the throttle member 9 will maintain the main passage of the air intake closed untilthe position (11 is reached. However, within this range the fuel injection pump adjusting member 3 is moved in such a manner by the peripheral surface of the cam body 2 moving in the direction of arrow 14 that the rate of fuel injection is increased, the rate. of increase, being selected in such a manner that an ignitable mixture is obtained at least at the moment at which the throttle member 9f reaches the position a and thecam body 2 reaches the position a Thus, an ignitable fuel/air mixture is obtained even before the rate of air fiow allowed to pass to the engine for idling purposes has been exceeded;

It will be understood that under conditions'prevailing with conventional equipment in which the amount of intake air required for idling is determined by limiting the closing movement of the throttling member in a PIG! new a accelerator means for permitting fuel flow to said engine 7 when said accelerator is in a position away from said idling position thereof; first air admission means for admitting air at an adjustably fixed rate sufficient to sustain idling of said engine; and second air admission means responsive to movement of said accelerator means for movement of said second air admission means through a plurality of closed positions in which no air is admitted by said second air admission means, and a plurality of open positions in which increasing amounts of air are adm tted to said engine when said accelerator means moves away from said idling position.

determined partially open position, any increase in the rate of fuel injection that starts from an engine speed exceeding the minimum speed required for idling will result in an immediate increase in the cross-sectional area of the air intake passage and thus the intake airflow. As a result it is not before a considerably greater'air flow prevails that an ignitable mixture will be obtained. In the chart represented in Fig; 4 the point at which an ignitable mixture is obtained, which point is associated with the speed 11 would not lie on the curve a; which, up to the speed n is, parallel to curve a but would lie on the dash-and-dot curve a which, in the case of the embodiment shown, would correspond .to a condition in which the throttling member has already been opened further. Therefore, the range of transition that would have to be passed before an ignitable mixture could be obtained would be considerably longer.

It will be understood that modifications'and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention, but it is understood that the application is to be limited only by the scope of the appended claims. a

I claim: a

1. In an idling arrangement for a fuel injection system in an internal combustion engine, in combination, 'accelerator means movable toward and away from an idling position; fuel supply means for supplying fuel to said engine; fuel flow control means responsive tothe speed of said engine when said accelerator means is in the idling position thereof for substantially shutting ofi fuel flow to said engine by means of said fuel supply means when the speed of said engine exceeds a predetermined idling speed, and responsive to movement of said accelerator means for permitting fuel flow to said engine when said accelerator is in a position away from said idling posi tion thereof; first air admission means for admitting air at a rate sufficient to sustain idling of said engine; and second air admission means responsive to movement of said accelerator means for movement of said secondair admission means through a plurality of closedpositions in which no air is admitted by said second air admission means, and a plurality of open positions in which increasing amounts of air are admitted to said engine when said accelerator means moves away from said idling position.

2(In an idling arrangement for a fuel injection sysf tern in an internal combustion engine, in combination,

3'. In an idling arrangement for a fuel injection system in an internal combustion engine, in combination, accelerator means movable toward and away from an idling position; fuel supply means for supplying fuel to said engine; fuel flowcontrol means responsive to the speed of said engine when said accelerator means is in the idling position thereof for substantially shutting off fuel flow to said engine by means of said fuel supply means when the speed of said engine exceeds a predetermined idling speed, and responsive to movement of said accelerator means for permitting fuel how to said engine when said accelerator is in a position away from said idling posi tion thereof; air admission means for admitting air at a rate suflicient to sustain idling-of said engine; and air valye means responsive to movement of said accelerator means for movement of said air valve means through a plurality of closed positions in which no air is admitted by said air valve means, and a plurality of open positions in which increasing amounts of air are admitted to said engine when said accelerator means moves away from said idling position.

,4. In an idling arrangement for a fuel injection system an internal combustion engine, in combination, accelerator means movable toward and away from an idling position; fuel supply means for supplying fuel to said engine; fuel flow control means responsive to the speed of said engine when said accelerator means is in the idling position thereof for substantially shutting off fuel flow to said engine by means of said fuel supply means when the speed of said engine exceeds a predeterminedtidling rality of open positions in which increasing amounts of air are admitted to said engine when said accelerator means moves away from said idling position.

5. In an idling arrangement for a fuelrinjection system inan internal combustion, engine, incombination, accel: erator means movable toward and away from an idling position; fuel supply means for supplying fuel tosaid engine; cam means movable responsive to the speed of said engine when said accelerator means is in the idling position thereof; actuating means operatively connected with said cam means for substantially shutting ofi fuel flow to said engine by means of said fuel supply means when the speed of said engine exceeds a predetermined idling speed, said cam means being responsive. to move ment of said accelerator means -for permitting fuel flow accelerator means movable toward and away ,from an 15 to said engine when said accelerator isin a position away aesaaro from said idling position thereof; first air admission means for admitting air at a rate suflicient to sustain idling of said engine; and second air admission means responsive to movement of said accelerator means for movement of said second air admission means through a plurality of closed positions in which no air is admitted by said second air admission means, and a plurality of open positions in which increasing amounts of air are admitted to said engine when said accelerator means moves away from said idling position.

6. In an idling arrangement for a fuel injection system in an internal combustion engine, in combinatiomaccelerator means movable toward and away from an idling position; fuel supply means for supplying fuel to said engine; a shaft rotatable responsive to the speed of said engine; cam means mounted on said shaft for jointv rotation and axially slidable thereon responsive to movement of said accelerator means; cam follower means cooperating with said cam means while said accelerator means is in the idling position thereof for substantially 8 shutting off fuel flow to said engine by means of said fuel supply means when the speed of said engine exceeds a predetermined idling speed, and responsive to axial movement of said cam means for permitting fuel flow to said engine when said accelerator is in a position away from said idling position thereof; first air admission means for admitting air at a rate sufficient to sustain idling of said engine; and second air admission means responsive to movement of said accelerator means for movement of said second air admission means through a plurality of closed positions in which no air is admitted by said second air admission means, and a plurality of open positions in which increasing amounts of air are admitted to said engine when said accelerator means moves away from said idling position.

References Cited in the file of this patent UNITED STATES PATENTS Schweizer et al. June 26, 1956 

